1. Field of The Invention
The present invention relates in general to measuring a part, such as a brake rotor, to determine its ability to damp vibrations, and particularly relates to a method for locating vibration antinodes on such parts and calculating vibration parameters around the antinodes. The invention is an improvement of the method described in U.S. Pat. No. 6,014,899.
2. Description of Prior Developments
Although the method of determining and quantifying vibration and noise suppression as described in U.S. Pat. No. 6,014,899, is most effective, it is somewhat time consuming to complete. That is, when the method of U.S. Pat. No. 6,014,899 is carried out, measurements of the slope of the vibration decay curve of a part are taken at close intervals around the circumference of the part. Each measurement can take a significant amount of time to complete. Moreover, this prior method is subject to certain inaccuracies created by modulated, nonlinear vibration decay curves. This modulation is created by two separate modes of vibration which are present in the excited part and which can lead to significant differences in vibration damping measurements and Q-factor calculations, depending on the location on the part at which the slope of the decay curve is measured.
In the method of U.S. Pat. No. 6,014,899, it is suggested to simply eliminate those calculated values of vibration damping, known as Q-factors, which significantly exceed or differ from the average Q-factor calculated for the part. (It has now been learned that such values typically occur around vibration nodes on the part where modulated vibration decay curves are common.) Although this prior technique of simply ignoring and excluding large variations in Q-factors from the Q-factor curve fit improves the accuracy of the calculation of the average Q-factor of the part, it does not reduce the time required to calculate the average Q-factor, nor does it eliminate the need to make Q-factor calculations at each test point.
Accordingly, a need exists for a method and apparatus for reducing the time required to calculate an average or other single value representative Q-factor of a part.
A further need exists for increasing the accuracy of Q-factor measurement.
A further need exists for avoiding the use of modulated decay curves in Q-factor calculations which previously reduced the accuracy of Q-factor calculations.
Yet a further need exists for a method of determining Q-factors on a part, such that modulated nonlinear decay curves are excluded from the Q-factor calculations.